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Guitar Amp Recording

In our quest for the ultimate electric guitar sound, SOS tested favourite recording techniques from over 40 top-flight producers and engineers. Hear for yourself the results that amazed us.

I love reading interviews with engineers and producers, but the more of them I read, the more I come up against the basic problem that my brain is like a sieve. I'm forever thinking to myself "I really must remember that technique", but unless I dash off and use it right away the knowledge just skips out of my ear and heads for the hills, probably glad to be free. And even if I vaguely remember reading a fascinating passage about de-essing nose-flutes, I'm damned if I can recall where I read it or who recommended it.

A few months ago, I decided that enough was enough, so I began to trawl systematically through Sound On Sound's interview archive, collating and comparing different producers' views on a variety of recording and mixing topics. Being a glutton for punishment, I also waded through the 35-odd interviews in Howard Massey's excellent book, Behind The Glass.

The first subject I concentrated on is (you guessed it) recording electric guitars. What became immediately apparent was that there was a huge range of different techniques being used, and also that there were strong differences of opinion between different professionals, which left the question 'who do I believe?' The only way I could answer that question was to put the different techniques into practice in the studio, and then A/B them to sort the sheep from the goats.

Now, I'm sure that you're all sensibly busying yourselves with making music, so your lives are, frankly, too short to be sifting through more than a half a million words of interviews. Therefore, I'm going to try to digest what I've discovered during this process for the benefit of those less sad than me! I'm not about to dictate which technique is 'best', though, because if reading this many interviews has taught me anything it is that people will always disagree on what constitutes a great sound. Instead I've recorded a number of different audio examples to allow you to judge for yourselves, just as I did, which techniques are likely to make a real difference to your own productions. I've peppered this article with a number of boxes giving details of these files.

I'll be referring to a lot of different producers in this article, and it's understandable that you may not have initially heard of some of them, even if you've probably heard some of their productions. To avoid an avalanche of parentheses, I've put a list of all the producers I mention into a box which runs across the bottom of this article. The box also includes a few of their most celebrated credits, so that you can have some idea of where each of them is coming from stylistically.

About the only thing that all these producers have tended to agree on across the board is that you should try to get your guitar sound as good as you can before you even think about recording. "The stupidest thing that any musician can do," remarks Tony Platt, "is to just plug in and play and say 'make that sound good'. It doesn't work like that. I will always say to the guitar player, for instance, 'Is that sound coming out of your amplifier the sound you want to hear? If it isn't, show me what it is and we'll try to get somewhere close to that before we even put a microphone on.' It's a waste of everybody's time to sit there tweaking stuff until somebody says 'Oh that's good.'"

There is clearly a great deal that the guitarist can do for the sound by changing guitars, strings and amps, but from the perspective of the recording engineer it's also important to think about how the guitar cab is interacting with the room it's in. For example, Roy Thomas Baker mentions that he sometimes sets up the same guitar cab in different rooms because of the effect on the sound. Even if you're restricted to one room, a number of producers suggest trying out different positions of the amp in the room. Tony Visconti: "It's not so much that you're miking a guitar — you're miking a guitar in a room. I had a cellist in here recently, and I moved her until I got a good sound. Once I put her in one particular corner, her cello just sang — the room just filled up with the low end, and the sound exploded! A person who hasn't had years of experience might not have thought of doing that, but I could tell there was something lacking when she was in the centre of the room. That's mic technique. It's not so much the instrument; the room is very much part of the sound."

One reason why the sound changes in different parts of a given room is that sound reflecting from room boundaries reaches your recording microphone later than the sound travelling directly from the amp, causing phase cancellation — in effect a series of peaks and dips in the recorded frequency response, the spacing of which is related to the delay between the direct and reflected sounds. Keith Olsen suggests lifting and/or tilting the amp to minimise the effects of phase cancellation. "Leo Fender put those legs on the sides of a Fender Twin, and he did it so the guy in the orchestra could actually hear it when he was playing soft. But the other reason is that when you put a mic up against an amp tilted that way... you don't get phase-cancellation problems off the floor and wall. Let's take it one step farther. Let's lift that speaker cabinet off the floor and put it up on something that is stable enough to be able to give the speakers a platform to work from, but where... the reflected sound is going to be so far down in volume to the direct, it's of no real consequence... All these things start adding together into mic technique, stuff that you learn over years."

Also using his room to advantage is Jay Graydon, who talks about placing a guitar amp on his studio's drum riser for certain sounds. "The riser eliminates low-end coupling with the floor. I am looking for a sweet mid-range tone, so as to not take up too much room in the track, meaning that I do not want low-end information for solos."

Several producers like to create larger-than-life recorded sounds by splitting the guitarist's instrument signal to several different amps, which are then recorded simultaneously. Joe Barresi is a devotee of this tactic, and uses a dedicated guitar splitter box, such as the Little Labs PCP Instrument Distro or Systematic Systems Guitar Splitter, for the purpose. "In choosing the amplifiers and speakers, it's important to remember that larger speakers give a more compact, tighter sound. A tiny amp turned all the way up will give a more blown-out sound."

Mike Hedges also uses this idea a great deal, and explains how it really comes into its own at the mix. "You've got two or three tracks of guitar: one clean, one medium — say, half-driven — and then one really driven. As the song progresses, you might use the nice clean track during the verse, as you're coming to the bridge you fade in the heavier guitar sound, then back it off a bit, into the chorus with everything full on, then back to the next verse and drop it all out. It's all done on one guitar track, so it doesn't sound like you've done 10 guitar overdubs. It has a different quality, it sounds like a live performance, but you've got real dynamics in the sounds. It's a very effective technique."

On a practical note, Steve Churchyard has this to add: "You'll want a good A/B box so that you can split the guitar feed to the two amps and obviously use the shortest [cable] run. Ideally have the amps in the control room and run the longer leads to the speakers."

When it comes to recording electric guitar, Jay Graydon's views on mic choice are pretty clear: "I have tried so many dynamic mics over the years, and always come back to the Shure SM57." He's not alone: this robust, cardioid, dynamic microphone is more often mentioned in relation to electric-guitar recording than any other.

Shure SM57.Sennheiser MD421.For a rock sound, many (though not all!) engineers will use a dynamic mic placed close to the speaker (sometimes on its own, sometimes in combination with other mics) like this Electrovoice RE20.Why such a strong preference? These days, force of habit has got to be part of the answer, but there is also a lot about the microphone's frequency response which suits guitar recording. For a start, the sub-200Hz response roll-off reduces low-end cabinet 'thumps', which might otherwise conflict with the kick drum and bass in the mix. This also compensates for proximity boost when the mic is used very close to the speaker cone. However, there's also a slight 'suckout' at 300-500Hz, an area where muddiness can easily occur, and a broad 2-12kHz presence peak, which adds bite and helps the guitars cut through the rest of the track.

Producers as varied as Chuck Ainlay, Mike Clink, Mike Hedges, Gil Norton, Bob Rock, Elliot Scheiner and Tony Visconti all claim to have recorded electric guitar using this mic alone, and it would probably be fair to say that it's often the first mic to come out of the locker for many more than these.

Sennheiser's cardioid MD421 crops up almost as frequently in interviews, and has a wider frequency response, none of the low mid-range suckout, and an even heftier sensitivity boost upwards of 1kHz. This microphone also has a larger diaphragm than the SM57, and the off-axis response anomalies of the larger diaphragm, in particular, give a different character to the sound. Although obviously very popular, this mic seems more often to be used in combination with other mics than on its own.

The same goes for Electrovoice's RE20, which counts Steve Albini, John Fry, and especially Glenn Kolotkin amongst its friends. "I like to use RE20s on most amplifiers when they're available", says Glenn, "because the quality is great and they can take really high levels. They're very directional and they're great for rock and roll." The mic also exhibits an unusually wide and flat frequency response and is specially designed to resist proximity effect.

Alan Parsons: "I always use condenser mics on a guitar amp, never dynamics — they're too telephoney. That's an unfair expression for a very good dynamic mic, but by comparison to a condenser, you're not going to get the bottom end." While this stance is more hard-line than that of most engineers, condenser mics are, of course, regularly used for recording electric guitars. However, in practice they rarely seem to be used on their own and are very often lined up alongside the trusty SM57.

Large-diaphragm models are popular, with Neumann mics particularly favoured. The famous U87 studio workhorse is probably the most commonly mentioned, but it's by no means the only contender. Eddie Kramer, Steve Albini and John Leckie single out its predecessor, the U67, for example, while both of the earlier U47 models (valve and FET) receive name checks from people such as Steven Street, Glenn Kolotkin, Butch Vig and Bruce Botnick (note that U47s were marketed under both Neumann and Telefunken brand-names, but they're essentially the same mics). Neumann aren't the only game in town, though: AKG's C414B-ULS is probably joint most popular large-diaphragm model alongside the U87.

Popular condensers: when it comes to condenser mics for guitar-cab miking, the AKG C414 (in its various flavours — the C414 B-ULS is pictured above left) and the Neumann U87 (centre) are both popular choices. Some producers also frequently look to the U87's predecessors, the U47 valve (pictured) and FET models, and the U67.The characteristics that producers most often seem to be looking for in these mics are their extended frequency response, especially at the low end, and the slightly softer, more diffuse sound imparted by the large diaphragm. These mics also tend to boost the 5-15kHz region, but this boost is rapidly lost as you move off-axis (it is inherently difficult to design a large-diaphragm capsule with an even off-axis frequency response).

Small-diaphragm condenser mics, on the other hand, tend to have flatter frequency plots and a better-behaved off-axis response, giving a sound sometimes described as more focused, but they seem to be less commonly chosen by the interviewees than large-diaphragm ones. Neumann's KM84 seems to be the most regular choice of small-diaphragm condenser, and numbers John Fry and Bill Price amongst its high-profile users, while Sennheiser's MKH40 warrants a particular mention from Mike Hedges: "I started using [these mics] when I was working with the Beautiful South. I started off with two and now have more than 20. I think they were originally designed for classical recording, because they have very high gain and very low noise. This means that you can get a very clean sound. They also accept massive amounts of volume, so you can put one against a guitar amp on full and it will take it." Hedge's concern about the ability of the microphone to handle the sheer volume of some guitar amps is echoed by several of the other producers, who make a point of mentioning that they switch in a condenser's 10dB pad when recording electric guitars.

Surprisingly, perhaps, given their reputation for fragility, ribbon mics also seem to be widely used for electric guitar, with models from Beyerdynamic, Coles, RCA and Royer all putting in appearances. Producers using ribbons include Thom Panunzio, Joe Barresi, Steve Albini, Ed Cherney, Bill Bottrell and Butch Vig — Eddie Kramer even goes as far as to say that "to me, the best guitar mic is the Beyer M160, which I've used for 30 years on Hendrix, on Zeppelin, on everybody."

One trait of most ribbon mics is the figure-of-eight polar response, and this is often exceptionally consistent across the frequency range. This polar pattern means, of course, that ribbons tend to pick up a little more room ambience than cardioids, given that the polar pattern is as sensitive behind the diaphragm as it is in front. Ribbon mics are also often characterised as sounding 'smoother' compared with typical condenser microphones, partly because their construction avoids the high-frequency diaphragm resonances normally inherent in condenser designs.

Even working on the assumption that you're only using one mic, the professionals have an awful lot to say about where you might put it. For a start, it seems to be fairly common practice to audition the different speaker cones of your guitar amp. "They're supposed to sound the same," says Roy Thomas Baker, "but if you're using a 4x12 cabinet, each of these four speakers may sound different."

While there's nothing necessarily wrong with plonking your mic right at the centre of the speaker cone if it gets what you're after, a lot of producers take the time to experiment with different positionings off axis, where the sound is typically warmer. Mike Hedges: "Depending on where you have [the mic] — outer speaker or inner speaker — you get the difference in tone from the edge of the speaker and the centre of the cone." In fact, Mike Clink also tries small changes in position even when working with basically on-axis sounds. "I'll point [the SM57] exactly dead on, though I might move it an inch or two to get the right sound."

Directional mics, such as cardioids and figure-of-eights, exhibit different frequency responses off axis — broadly speaking, off-axis sounds tend to be duller, although it's a complex effect which is different for each model. Professional producers are well aware of this, and employ the effect to refine their sounds. For instance, Chuck Ainlay comments "I'll usually start with a [Shure SM57] on the amp; but not straight on axis with the middle of the speaker; it's usually off-centre, angled towards the middle of the speaker and generally just off the grille." Jay Graydon refers to a fairly similar setup: "I position the mic about one inch left of the edge of the speaker-cone centre, using a 22-degree angle, and about one inch back from the grille cloth." Andy Johns, on the other hand, has said that "the miking technique I used on electric guitars for years was two [Shure SM57s], one straight on, and one at 45 degrees. Put 'em together, and it always works."

The question of how far away to place your mic really divides opinions. While Chuck Ainlay's 'just off the grille' seems to express the majority view, Bill Price preferred a position six inches away on the Sex Pistols sessions, while Steve Albini usually starts from around 10-12 inches away. Alan Parsons, on the other hand, avoids close placements: "Every engineer I've ever come across has always had the mic touching the cloth, and the first thing I do is move it away literally a foot. Let's hear what the amplifier sounds like, not what the cabinet sounds like... I might have it even further away if it's a really loud 4x12 cabinet — as much as four feet away." Ben Hillier also extols the benefits of more distant placements, up to six to eight feet, when he's trying to capture his favourite 'amp in a room' sound.

One of the things that initially surprised me was that coincident dual-mic techniques, where the two mics are placed as close as possible to each other to minimise phase cancellation between them, actually appear to be more commonly used than single-mic techniques. John Leckie explains: "There's an amazing difference in the sound and colouration you get from adjusting the balance of each of the mics, and you can get radically different textures depending on your mix of the two."

The majority of favoured mic pairs seem to include the trusty SM57, but its most popular partner appears to be the larger-diaphragm MD421 — users include Bob Rock, Bruce Fairbairn, Alan Winstanley, Joe Barresi, Simon Dawson, Stephen Street and The Matrix. Also high on the list is the pairing of the SM57 with a large-diaphragm condenser of some type, and Steve Churchyard, Toni Visconti, Jim Scott, Stephen Street, and John Leckie all name-check the U87 in this role.

However, John Leckie states an interesting preference for an SM58 and U67 rig instead: "SM57s tend to be that little bit brighter than the SM58, which really isn't what you want when you're miking up an electric guitar amp. You really want to pick up a flat signal, an 'unstimulated' signal I suppose is the word... The U67 gives you the warmth and a broader sound."

Referring to this setup, Leckie also explains more about what makes double-miking so powerful: "If you brighten up the U67, it's totally different to brightening up the SM58, so sometimes I'll add a little brightness to the 67 and a little compression. But between that combination, I find I can get pretty much everything I need. They're rarely used at equal level; sometimes I'll favour the SM58 with the U67 at 10-15dB down. Even 20-30dB down, just bringing it in, it's amazing the different colour you get — how much the tone of the guitar changes."

Coupling an SM57 with a small-diaphragm KM84 condenser finds favour with Bill Price and John Fry, while Mike Hedges chooses his favourite Sennheiser MKH40. Bill Price also mentions the importance of finding a very close phase match between the two microphones. "What one had to do was balance those mics equally, grab a pair of headphones out in the studio that were turned up nice and loud, and fractionally position one of the mics so that they were perfectly in phase at high frequencies, because if you had one mic five inches away and the other six inches away you'd obviously get really bad phase shift that would take the top off the guitar sound."

Beyond specific favoured mics, a number of engineers also mention more general principles when choosing pairs of mics for guitar recording. Jim Scott and Stephen Street both mention using a 'cheap' or 'bad' mic with a good mic (both give the SM57+U87 combination as an example). "Between the two you can find the ideal sound," remarks Jim, "and you can get brightness and fullness."

Steve Albini, on the other hand, finds it useful to think in terms of blending 'bright' and 'dark' mics. "Normally I'll have two microphones on each cabinet, a dark mic and a bright mic, say a ribbon microphone and a condenser, or two different condensers with different characters." Eddie Kramer's discussion of his Hendrix sessions reveals a similar preference: "Generally speaking, it was either a U67 or a Beyerdynamic M160, or a combination of both, which I still use today. It might be slightly different, of course, but the basic principle's the same — a ribbon and a condenser."

Although a lot of engineers prefer to mic up the single, best-sounding speaker cone of a multi-speaker cab, some blend the sounds of more than one. Steve Churchyard: "If I'm using a 4x12 cabinet, I find two of the best-sounding speakers, and I'll put an SM57 right on axis and right on the cone of both those guys. Then I'll mix them in the control room, combine the two together. It seems a little different than just using one mic. It's not twice as good, but it's just mixing the character of two different speakers."

While recording AC/DC's Back In Black, Tony Platt used a pair of condenser mics to pick up different speaker cones and give a wider sound to each guitar: "I developed a technique for recording guitars with two microphones roughly pointing at different speakers, which can be spread out in the stereo mix so it's not just a series of mono point sources. It makes for a more open-sounding guitar. That sound suited their particular technique, which involved Angus and Malcolm playing the same chords but with different inversions to get a very big unison guitar sound."

Hugh Padgham adopted a similar tactic for recording Andy Summers' Roland JC120 when working with the Police: "The chorus [was] always switched on in order to produce the slightly out-of-tune guitar sound that was all the rage during the early '80s. The amp's two 12-inch speakers would each be close-miked with a Sennheiser MD421, panned left and right — one speaker would produce a straight signal while the other would be chorused, and these would sometimes be double-tracked the other way around in order to produce an especially wide stereo picture."

Of course, no-one says you have to use the same mic on each speaker cone. For example the SOS interview with Toby Wright shows an SM57 and an MD421 on separate speakers, and Don Smith mentioned using an SM57 and an AKG C451 on separate speakers when recording Keith Richards. Sylvia Massy Shivy also uses the SM57+MD421 combination, but sounds a note of caution when deciding on the exact positioning of the mics: "You have to be very careful with phase, just check it until the signal is the strongest."

"I've always thought that most people mic amps too closely," comments Alan Parsons. "They supposedly make up with an ambient mic, but I much prefer to find a mic position that works and process that, rather than mix in too much ambience." Despite Parsons' disapproval, though, a lot of the engineers I researched divulged that they use additional ambient mics to capture more of the sound of the room in which the guitar cab was recorded.

For example, Al Schmitt starts with the traditional SM57 close mic, on axis but a little off the centre of the cone. "Then I'll put a really good mic up — maybe a Neumann U67 or an M50 — for the room... It could be anywhere from 15 to 20 feet away." It's worth noting that the M50 is an omni microphone and, although the omni polar pattern is only very occasionally mentioned for close-miking, it makes a much more sensible choice for capturing natural room ambience.

Tony Visconti is also into using ambient mics: "I'm very much a fan of the room sound, too. I always record it if it's a real heavy rock guitar with power chords and crunches and all. I'll go around the room and clap my hands and I say, 'Put the mics there, that's it.' Quite often, I'll turn the room mic towards the studio window, and you'll get a reflection of the guitar sound — not directly facing it, because you're looking for reflections." Although he states in the same interview that he'll try to use a pair of U87s for ambience if possible, he's also mentioned elsewhere using PZM mics as an alternative.

Perhaps the most dramatic of ambient mic techniques, though, comes courtesy of Chris Tsangarides. His 'Vortex' involves using studio screens to build 30-foot-long walls along each side of the guitar cabinet, creating a flare shape (apparently inspired by the shape of a bass bin). Within this flare, he places a close condenser mic and typically another couple of condenser mics with different distant positionings, perhaps at 15 and 30 feet away. "I walk around while the guy's playing and find a sweet spot and put the mic there", says Chris.

By panning the distant mics to the opposite side of the mix from the close mic, you can create interesting panning effects for solos. "If it's a rhythm part, you get this huge sound because the whole thing is spread across the stereo spectrum." When double-tracking lead or rhythm parts, a useful trick is to reverse the panning of the direct and distant mics. "If there were two guitarists in a band, I would record them like that, so you got a wall of sound that had a transparency that would allow the drums and bass to come through."

While experimenting with the Vortex for this article, I was impressed by quite how well the ambient mics seemed to turn a close-miked guitar sound into something that sounded like it was on a record, but the downside of this approach for most home recordists will be that the Vortex is not easy to recreate in a smaller studio — so I thought I'd pass on some ways I found to make it more manageable on a smaller scale. One problem most small studios have is that they don't have large numbers of screens, but in practice I found that I was able to get decent results by putting the guitar cab in the corner of the room and using one or both of the room boundaries in place of the screens. Visconti's trick of aiming ambient mics at the studio glass also turned out to be handy to increase the apparent distance of the farther ambient mic.

This great book of interviews is, in my opinion, one of only a handful of truly essential record-production books, and is packed with down-to-earth recording advice, as well as discussions of the art of production. In addition to the interviews I've referred to in this article, the book also features such greats as Glen Ballard, Arif Mardin, Brian Wilson, Phil Ramone, Mitchell Froom, George Martin and Geoff Emerick, and one of the strengths of Massey's approach is that he often asks them similar questions, which makes for interesting comparisons.

There are also two interesting panel discussions where several of the featured producers discuss their trade head-to-head.

Let's look at how the professionals go about combining the close and ambient techniques we've looked at so far, in order to create specific custom setups for different recordings. Joe Barresi, for example, relies heavily on the trusty SM57 and MD421 combination, but he'll choose from a variety of other mics to give character to particular sounds. "The two microphones I use most for recording electric guitars are the Shure SM57 and the Sennheiser MD421, often both, close up, placed at the edge of the speaker, where the speaker centre meets the cone, or, if I'm looking for a more bright sound, dead centre. When I want more low end, I may have an AKG C414 on there, and when I'm after a little more personality, a Neumann U87, backed up a foot, or a ribbon mic, like the Royer 122, or an RCA BK5 or 77."

Eddie Kramer has a slightly different approach, working from a familiar setup of favourite close and ambient mics (including the Beyerdynamic M160 ribbon mic) and then mixing them together to taste. "I use a three-mic technique: an SM57, an MD421 and an M160, all in a very tight pattern. Then I can pick and choose the tone quality, because each mic is totally different. I combine these together, and then I put a U67 away from the amp to get the ambience."

For his work on Supernatural, Glenn Kolotkin turned to elaborate multi-miking as a way of managing Carlos Santana's complicated setup. "I used multiple microphones on Carlos' guitars: Electrovoice RE20s close, Neumann U47s further away, an SM56, U87s. He was playing through an assortment of amplifiers at the same time, and by using multiple microphones I was able to get just the right blend."

Complex though some of these techniques are, probably the most powerful use of multi-miking I've encountered during my investigations comes courtesy of Jack Douglas, who makes creative use of phase cancellation between microphones. "For guitar overdubs, the best EQ in the world is the phase EQ, which you get by using multiple mics on a speaker. For example, take a Shure SM57, a Sennheiser MD421 and your favourite condenser, and set them up in a triangle with the two dynamics at an angle up against the grille, but off axis. Then take your favourite condenser mic, put a 10dB pad on it, and place it about a foot away, facing the speaker, on axis.

"Bring up one mic at a time and get it to optimum level on your board. To check that they're all in phase, make sure the signal is adding and not subtracting as you add in the other mics. If not... reverse the phase. Then start to put up each mic, one at a time... as you move the faders back and forth, you'll hear the greatest EQ, because of the phase relationship... Then if you flip the phase on one of the mics, you can really have some fun — it'll act like a filter."

Having tried out this technique, I have to say that it's something of a revelation to hear the enormous range of radically different sounds it makes available. When you start inverting the phase of a mic, it sounds like the most extreme EQ you've ever heard, which means that you can substantially reinvent guitar sounds at mixdown without using any heavy processing. For even more sonic mileage, you can also take a leaf out of John Leckie's book and process each of the three mic signals independently.

Jack Douglas also points out a beneficial side-effect, in his experience, of recordings made using the phase EQ approach: "When you build a mix — I don't care if it's four tracks, eight tracks, or 96 — the real nightmare is when you put something up and the only way you can hear it is by blasting it. There's nothing worse than putting up something you're excited about, and it's gone. If you [record guitars] like this, I guarantee that as soon as you put the sound in the mix it will be there. Not only that, it won't wipe out everything else in the mix, because it will have such a separate and distinct character."

Being by nature rather sceptical, I have to admit to initially dismissing many of the recording methods in this article as 'studio snake oil', and because there was usually too little time during my own sessions to experiment with new ideas, I'd usually end up with an SM57 glued to the speaker grille by default. Taking the time out to trial the above techniques in the studio showed me quite how much I had been missing — not only much better raw recordings, but also tremendous extra flexibility at mixdown. But don't take it from me — listen to the audio examples for yourself and make up your own mind. If they don't expand your recording horizons, I'll eat my SM57...

Thanks to Tom Adams, Hills Road Sixth Form College, and Paul Nunnington at Sennheiser UK for their assistance in creating the audio files for this article.

This box contains a list of the producers mentioned in this article. The source of the interview is in parentheses after each name, in case you fancy reading more about them and, for reference, I have also listed some of the most influential recordings they've been involved with.